The present invention relates to an arrangement for maintaining a desired temperature of a battery in a vehicle.
Hybrid vehicles powered by electricity in combination with some other form of fuel are equipped with one or more batteries to store electrical energy and with regulating equipment to regulate the flow of electrical energy between the battery and an electrical machine which alternately serves as motor and generator, depending on the vehicle's operating state. The battery and the regulating equipment are inevitably subject to a certain warming during operation. For optimum operation of the battery and the regulating equipment they should not be warmed to too high a temperature. Depending on its type, the battery should not be warmed above a highest temperature, e.g. of the order of 45° C. The regulating equipment may be warmed to a somewhat higher temperature. The battery and the regulating equipment therefore need cooling during operation. Most batteries have an optimum operating temperature between 20 and 30° C. The battery may therefore also need to be warmed at times when it is at too low a temperature.
A known practice is to use air to cool batteries in hybrid vehicles, but the air needs to be of high quality because batteries are sensitive to pollutants and moisture. Accordingly, a known practice is for the battery to be situated in the driving cab space of vehicles, where the air is of high quality and at a suitable temperature. In such cases, a fan may generate a cooling air flow through the battery. However, it is for various reasons desirable for the battery to be situated elsewhere in the vehicle than in the cab space. Another known practice is to place the battery in the vehicle's engine space. Since the air in the engine space of a vehicle is more or less polluted, it cannot be used directly for cooling battery. In such cases, the battery is encased in a suitable way and an AC installation is used to cool it. When the battery needs warming, this can be effected by means of electrical components or by coolant from the cooling system which cools the engine. A relatively complex arrangement is thus required to maintain a desired temperature of a battery in an engine space. Using an AC installation to cool a battery during operation involves also supply of a relatively large amount of energy.